Understanding Reflection in Java: Accessing Class Information at Runtime

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Ravi Vishwakarma · Answer

Reflection in Java is a effective function that lets in programs to look at and manage
classes, methods, fields, 
and constructors at runtime — although their names are not known until execution.
1. What Can You Do With Reflection?
Using reflection, you can:
Get information about a class (name, methods, fields, constructors, etc.)Instantiate objects dynamicallyInvoke methods dynamicallyAccess or modify fields, even private ones
2. How to Use Reflection
Reflection is available in the java.lang.reflect package. You typically start by getting the
Class object of the target class.
Classandlt;?andgt; clazz = Class.forName("com.example.MyClass");
Or, if you have the object:
Classandlt;?andgt; clazz = myObject.getClass();
3. Examples of Using Reflection
a. Get Class Information
public class Demo {
    public int num;
    private String text;
    public void sayHello() {
        System.out.println("Hello");
    }
}
public class ReflectionInfo {
    public static void main(String[] args) {
        Classandlt;?andgt; clazz = Demo.class;
        System.out.println("Class Name: " + clazz.getName());
        System.out.println("
Fields:");
        for (Field field : clazz.getDeclaredFields()) {
            System.out.println(field.getName());
        }
        System.out.println("
Methods:");
        for (Method method : clazz.getDeclaredMethods()) {
            System.out.println(method.getName());
        }
    }
}
b. Accessing and Modifying Fields
import java.lang.reflect.Field;
public class ReflectionFieldAccess {
    public static void main(String[] args) throws Exception {
        Demo demo = new Demo();
        Classandlt;?andgt; clazz = demo.getClass();
        Field field = clazz.getDeclaredField("text");
        field.setAccessible(true); // Allow access to private field
        field.set(demo, "Reflection Rocks!");
        System.out.println("Value of text: " + field.get(demo));
    }
}
c. Invoking Methods Dynamically
import java.lang.reflect.Method;
public class ReflectionMethodInvoke {
    public static void main(String[] args) throws Exception {
        Demo demo = new Demo();
        Classandlt;?andgt; clazz = demo.getClass();
        Method method = clazz.getDeclaredMethod("sayHello");
        method.invoke(demo); // calls demo.sayHello()
    }
}
d. Creating Object Using Constructor
import java.lang.reflect.Constructor;
public class ReflectionConstructor {
    public static void main(String[] args) throws Exception {
        Classandlt;?andgt; clazz = Demo.class;
        Constructorandlt;?andgt; constructor = clazz.getConstructor();
        Object obj = constructor.newInstance();
        System.out.println("Object created: " + obj);
    }
}
4. Important Notes
Reflection breaks encapsulation and should be used carefully.It can lead to performance overhead.It's frequently used in frameworks like Spring, Hibernate, and JUnit.Reflection can get admission to private participants, but you need to apply setAccessible(actual).
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Understanding Reflection in Java: Accessing Class Information at Runtime

Ravi Vishwakarma

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1 Answers

1. What Can You Do With Reflection?

2. How to Use Reflection

3. Examples of Using Reflection

a. Get Class Information

b. Accessing and Modifying Fields

c. Invoking Methods Dynamically

d. Creating Object Using Constructor

4. Important Notes

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